1. Field of the Invention
The present invention relates to wheel rim forming machines and, more particularly, to a top roll exchanging apparatus for a wheel rim forming machine.
2. Description of the Related Art
Vehicle wheels are conventionally manufactured on a disk wheel manufacture line by the following series of steps: First, a long plate of predetermined width is cut to a specified length and rolled to form a tube. The end portions of the rolled plate are then butt welded to form a one piece cylindrical element. The cylindrical element is conveyed to a flaring machine where both axial end portions of the cylindrical element is flared. The flared cylindrical element is conveyed to a wheel rim forming station which usually comprises a plurality of wheel rim forming machines arranged in series where it is press formed to produce a required rim shape. After the formation of the rim shape, the rim element is conveyed to a disk insertion station where a disk which has been manufactured on another line is inserted into the rim element. The rim element and the disk are conveyed to a welding station where they are welded together to form a disk wheel. Finally, the disk wheel is painted.
Since the diameter, width, thickness and shape of the rim element vary according to the type of wheel to be manufactured, the top roll and bottom roll of the wheel rim forming machine between which the rim element is press formed must be changed in accordance with a change in the type of wheel to be manufactured. Exchange of the bottom roll is relatively easy, because the bottom roll and a bottom roll shaft for supporting the bottom roll are axially divided to two members, respectively, and because the bottom roll shaft are supported by a fixed frame. However, exchange of the top roll is quite difficult because the top roll is supported by a rather complicated vertically driven frame structure.
More particularly, heretofore, the top roll has been exchanged as follows: First, one of the bearing devices which supports the end portions of the top roll shaft mounted with the top roll is removed so that the top roll shaft is supported only by the other bearing device in a cantilevered manner. Next, the top roll is slid along the top roll shaft and is removed from the free end thereof. Another top roll is then mounted onto the top roll shaft from the free end of the shaft. The removed bearing device is returned to its original position so that the top roll shaft is again supported at both end portions thereof. Each of the foregoing steps are performed by hand because the support structure of the top roll shaft is so complicated and no easier exchanging procedure existed. Since the bearing device and the top roll are very heavy, handling of the same is difficult and dangerous, and exchanging of the top roll takes a relatively long period of time.